Effects of Quercus emoryi trees on microclimate, precipitation distribution, and herbs in a semi-arid savanna

Abstract

This study evaluated the effects of individual trees (5-70 m² canopy area) on precipitation distribution, bulk density, soil moisture, soil temperature, elevational gradients, and herbaceous species composition and biomass in a Ouercus emoryi Torr. savanna in southeastern Arizona. Throughfall was influenced by tree size and storm size for precipitation events less than 3 cm. Nonlinear regression showed an exponential relationship between storm size and stemflow; storm size explained 67% of the variability in stemf low. Tree size was linearly related to stemf low, and explained an additional 5% of the variability. Location beneath trees and between-tree variability influenced soil moisture and temperature. These factors influenced soil temperature on more sampling dates than soil moisture. Temperatures were cooler beneath tree canopies in summer and warmer in winter. Herbaceous biomass was reduced by tree canopies, but composition was not influenced by trees.